I have similar trouble. My Kia Rio 2006 LX won't start easily after I fill the tank.
I have to crank the engine for 5-10 seconds and give it lots of gas before the engine starts. Then I have to maintain lots of revs as the engine won't idle. I then have to drive about 2 miles before the engine is back to normal.
My mechanic suggested that I take the car to Kia and have them apply an ECM update as described in this Service Bulletin:
Make : KIA Model : RIO Year : 2006
Manufacturer : KIA MOTORS CORPORATION
Service Bulletin Number : TSB-033 Date of Bulletin : APR 01, 2010
NHTSA Item Number : 10032713
Component : ENGINE AND ENGINE COOLING:ENGINE
KIA: ECM UPGRADE-MIL ON WITH DTC P0300, P0128, P0140, P0442 & P0461. VEHICLES MAY EXPERIENCE A ROUGH IDLE DURING INITIAL COLD START UP PERIOD AND/OR ILLUMINATE THE MIL. *PE UPDATED 10/29/10. *PE
I went to my local Kia Dealer and the service center looked at me like I was stupid when I asked for the update. I was also told I was "shit out of luck" because the check engine light wasn't on.
Has anyone had this update preformed? If so how can I get Kia to do it without ripping me off?